Larger image to save or print.Greenhouse gases trap heat and make the planet warmer. Human activities are responsible for almost all of the increase in greenhouse gases in the atmosphere over the last 150 years.1 The largest source of greenhouse gas emissions from human activities in the United States is from burning fossil fuels for electricity, heat, and transportation.

Commercial and Residential (11 percent of 2016 greenhouse gas emissions) – Greenhouse gas emissions from businesses and homes arise primarily from fossil fuels burned for heat, the use of certain products that contain greenhouse gases, and the handling of waste.

Land Use and Forestry (offset of 11 percent of 2016 greenhouse gas emissions) – Land areas can act as a sink (absorbing CO2 from the atmosphere) or a source of greenhouse gas emissions. In the United States, since 1990, managed forests and other lands have absorbed more CO2 from the atmosphere than they emit.

Emissions and Trends

Since 1990, gross U.S. greenhouse gas emissions have increased by about 2 percent. From year to year, emissions can rise and fall due to changes in the economy, the price of fuel, and other factors. In 2016, U.S. greenhouse gas emissions decreased compared to 2015 levels. This decrease was largely driven by a decrease in emissions from fossil fuel combustion, which was a result of multiple factors including substitution from coal to natural gas consumption in the electric power sector; warmer winter conditions that reduced demand for heating fuel in the residential and commercial sectors.

Larger image to save or print.The Electricity sector involves the generation, transmission, and distribution of electricity. Carbon dioxide (CO2) makes up the vast majority of greenhouse gas emissions from the sector, but smaller amounts of methane (CH4) and nitrous oxide (N2O) are also emitted. These gases are released during the combustion of fossil fuels, such as coal, oil, and natural gas, to produce electricity. Less than 1 percent of greenhouse gas emissions from the sector come from sulfur hexafluoride (SF6), an insulating chemical used in electricity transmission and distribution equipment.

Greenhouse Gas Emissions in the Electricity Sector by Fuel Source

Coal combustion is more carbon intensive than burning natural gas or petroleum for electricity. Although coal accounted for about 67 percent of CO2 emissions from the sector, it represented only about 32 percent of the electricity generated in the United States in 2016. Another 33 percent of electricity generated in 2016 was generated using natural gas, an increase relative to 2015. Petroleum accounted for less than 1 percent of electricity generation in 2016. The remaining generation in 2016 came from non-fossil fuel sources including nuclear (about 21 percent) and renewable sources (about 14 percent), which include hydroelectricity, biomass, wind, and solar.1 These other sources usually release fewer greenhouse gas emissions than fossil fuel combustion, if any emissions at all.

Emissions and Trends

In 2016, the electricity sector was the second largest source of U.S. greenhouse gas emissions, accounting for about 28.4 percent of the U.S. total. Greenhouse gas emissions from electricity have decreased by about 1 percent since 1990 due to fuel switching to lower emitting sources of electricity production.

Greenhouse Gas Emissions by Electricity End-Use

Larger image to save or print.Electricity is consumed by other sectors—in homes, businesses, and factories. Therefore, it is possible to attribute the greenhouse gas emissions from electricity production to the sectors that use the electricity. Looking at greenhouse gas emissions by end-use sector can help us understand energy demand across sectors and changes in energy use over time.

When emissions from electricity are allocated to the end-use sector, industrial activities account for a much larger share of U.S. greenhouse gas emissions. Emissions from commercial and residential buildings also increase substantially when emissions from electricity are included, due to their relatively large share of electricity consumption (e.g., lighting and appliances).

Larger image to save or print.The Transportation sector includes the movement of people and goods by cars, trucks, trains, ships, airplanes, and other vehicles. The majority of greenhouse gas emissions from transportation are carbon dioxide (CO2) emissions resulting from the combustion of petroleum-based products, like gasoline, in internal combustion engines. The largest sources of transportation-related greenhouse gas emissions include passenger cars and light-duty trucks, including sport utility vehicles, pickup trucks, and minivans. These sources account for over half of the emissions from the transportation sector. The remaining greenhouse gas emissions from the transportation sector come from other modes of transportation, including freight trucks, commercial aircraft, ships, boats, and trains, as well as pipelines and lubricants.

Relatively small amounts of methane (CH4) and nitrous oxide (N2O) are emitted during fuel combustion. In addition, a small amount of hydrofluorocarbon (HFC) emissions are included in the Transportation sector. These emissions result from the use of mobile air conditioners and refrigerated transport.

Emissions and Trends

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In 2016, greenhouse gas emissions from transportation accounted for about 28.5 percent of total U.S. greenhouse gas emissions, making it the largest contributor of U.S. greenhouse gas emissions. In terms of the overall trend, from 1990 to 2016, total transportation emissions increased due, in large part, to increased demand for travel. The number of vehicle miles traveled (VMT) by light-duty motor vehicles (passenger cars and light-duty trucks) increased by approximately 45 percent from 1990 to 2016, as a result of a confluence of factors including population growth, economic growth, urban sprawl, and periods of low fuel prices. Between 1990 and 2004, average fuel economy among new vehicles sold annually declined, as sales of light-duty trucks increased. Starting in 2005, average new vehicle fuel economy began to increase while light-duty VMT grew only modestly for much of the period. Average new vehicle fuel economy has improved almost every year since 2005, and the truck share is about 43 percent of new vehicles in model year 2015.

Emissions involved in the consumption of electricity for transportation activities are included above, but not shown separately (as was done for other sectors). These indirect emissions are negligible, accounting for less than 1 percent of the total emissions shown in the graph.

Using fuels that emit less CO2 than fuels currently being used. Alternative sources can include biofuels; hydrogen; electricity from renewable sources, such as wind and solar; or fossil fuels that are less CO2-intensive than the fuels that they replace.

Larger image to save or print.The Industry sector produces the goods and raw materials we use every day. The greenhouse gases emitted during industrial production are split into two categories: direct emissions that are produced at the facility, and indirect emissions that occur off site, but are associated with the facility's use of energy.

Direct emissions are produced by burning fuel for power or heat, through chemical reactions, and from leaks from industrial processes or equipment. Most direct emissions come from the consumption of fossil fuels for energy. A smaller amount, roughly a third, come from leaks from natural gas and petroleum systems, the use of fuels in production (e.g., petroleum products used to make plastics), and chemical reactions during the production of chemicals, iron and steel, and cement.

Indirect emissions are produced by burning fossil fuel at a power plant to make electricity, which is then used by an industrial facility to power industrial buildings and machinery.

Emissions and Trends

In 2016, direct industrial greenhouse gas emissions accounted for approximately 22 percent of total U.S. greenhouse gas emissions, making it the third largest contributor to U.S. greenhouse gas emissions, after the Electricity and Transportation sectors. If both direct and indirect emissions associated with electricity use are included, industry's share of total U.S. greenhouse gas emissions in 2016 was 29 percent, making it the largest contributor of greenhouse gases of any sector. Greenhouse gas emissions from industry have declined by almost 14 percent since 1990, while emissions from most other sectors have increased.

Upgrading to more efficient industrial technology.
EPA's ENERGY STAR® program helps industries become more energy-efficient.

Identifying the ways that manufacturers(87 pp, 1 M, About PDF) can use less energy to light and heat factories or to run equipment.

Fuel Switching

Switching to fuels that result in less CO2 emissions but the same amount of energy, when combusted.

Using natural gas instead of coal to run machinery.

Recycling

Producing industrial products from materials that are recycled or renewable, rather than producing new products from raw materials.

Using scrap steel and scrap aluminum as opposed to smelting new aluminum or forging new steel.

Training and Awareness

Making companies and workers aware of the steps to reduce or prevent emissions leaks from equipment.
EPA has a variety of voluntary programs that provide resources for training and other steps for reducing emissions. EPA supports programs for the aluminum, semiconductor, and magnesium industries.

Instituting handling policies and procedures for perfluorocarbons (PFCs), hydrofluorocarbons (HFCs), and sulfur hexafluoride (SF6) that reduce occurrences of accidental releases and leaks from containers and equipment.

Larger image to save or printThe residential and commercial sectors include all homes and commercial businesses (excluding agricultural and industrial activities). Greenhouse gas emissions from this sector come from direct emissions including fossil fuel combustion for heating and cooking needs, management of waste and wastewater, and leaks from refrigerants in homes and businesses as well as indirect emissions that occur offsite but are associated with use of electricity consumed by homes and businesses.

Direct emissions are produced from residential and commercial activities in a variety of ways:

Combustion of natural gas and petroleum products for heating and cooking needs emits carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O). Emissions from natural gas consumption represent about 78 percent of the direct fossil fuel CO2 emissions from the residential and commercial sectors. Coal consumption is a minor component of energy use in both of these sectors.

Organic waste sent to landfills emits CH4.

Wastewater treatment plants emit CH4 and N2O.

Fluorinated gases (mainly hydrofluorocarbons, or HFCs) used in air conditioning and refrigeration systems can be released during servicing or from leaking equipment.

Indirect emissions are produced by burning fossil fuel at a power plant to make electricity, which is then used in residential and commercial activities such as lighting and for appliances.

Emissions and Trends

In 2016, direct greenhouse gas emissions from homes and businesses accounted for approximately 11 percent of total U.S. greenhouse gas emissions. Greenhouse gas emissions from homes and businesses vary from year to year based on short-term fluctuations in energy consumption caused primarily by weather conditions. Total residential and commercial greenhouse gas emissions in 2016 have increased by about 7 percent since 1990. Greenhouse gas emissions from on-site direct emissions in homes and businesses have decreased by about 3 percent since 1990. Additionally, indirect emissions from electricity use by homes and businesses have increased by 14 percent since 1990, due to increasing electricity consumption for lighting, heating, air conditioning, and appliances.

Examples of Reduction Opportunities in the Residential and Commercial Sector

Type

How Emissions Are Reduced

Examples

Homes and Commercial Buildings

Reducing energy use through energy efficiency.

Homes and commercial buildings use large amounts of energy for heating, cooling, lighting, and other functions. "Green building" techniques and retrofits can allow new and existing buildings to use less energy to accomplish the same functions, leading to fewer greenhouse gas emissions. Techniques to improve building energy efficiency include better insulation; more energy-efficient heating, cooling, ventilation, and refrigeration systems; efficient fluorescent lighting; passive heating and lighting to take advantage of sunlight; and the purchase of energy-efficient appliances and electronics. Learn more about ENERGY STAR®.

Wastewater Treatment

Making water and wastewater systems more energy-efficient.

Drinking water and wastewater systems account for approximately 3 percent to 4 percent of energy use in the United States. Studies estimate potential savings of 15 percent to 30 percent that are "readily achievable" in water and wastewater plants.1
Learn more about Energy Efficiency for Water and Wastewater Utilities.

Waste Management

Reducing solid waste sent to landfills.
Capturing and using methane produced in current landfills.

Landfill gas is the natural byproduct of the decomposition of solid waste in landfills. It primarily consists of CO2 and CH4.
Well established, low-cost methods to reduce greenhouse gases from consumer waste exist, including recycling programs, waste reduction programs, and landfill methane capture programs.

Commonly used refrigerants include ozone-depleting hydrochlorofluorocarbon (HCFC) refrigerants, often HCFC-22, and blends consisting entirely or primarily of hydrofluorocarbons (HFCs), both of which are potent greenhouse gases. In recent years there have been several advancements in refrigeration technology that can help food retailers reduce both refrigerant charges and refrigerant emissions.
Learn more about EPA's GreenChill Program to reduce greenhouse gas emissions from commercial refrigerators.

Various management practices on agricultural soils can lead to increased availability of nitrogen in the soil and result in emissions of nitrous oxide (N2O). Specific activities that contribute to N2O emissions from agricultural lands include the application of synthetic and organic fertilizers, the growth of nitrogen-fixing crops, the drainage of organic soil, and irrigation practices. Management of agricultural soils accounts for over half of the emissions from the Agriculture economic sector.*

Livestock, especially ruminants such as cattle, produce methane (CH4) as part of their normal digestive processes. This process is called enteric fermentation, and it represents almost one third of the emissions from the Agriculture economic sector.

The way in which manure from livestock is managed also contributes to CH4 and N2O emissions. Different manure treatment and storage methods affect how much of these greenhouse gases are produced. Manure management accounts for about 15 percent of the total greenhouse gas emissions from the Agriculture economic sector in the United States.

Smaller sources of agricultural emissions include CO2 from liming and urea application, CH4 from rice cultivation, and burning crop residues, which produces CH4 and N2O.

Emissions and Trends

In 2016, greenhouse gas emissions from the agriculture economic sector accounted for approximately 9 percent of total U.S. greenhouse gas emissions. Greenhouse gas emissions from agriculture have increased by approximately 17 percent since 1990. One driver for this increase has been the 68 percent growth in combined CH4 and N2O emissions from livestock manure management systems, reflecting the increased use of emission-intensive liquid systems over this time period. Emissions from other agricultural sources have either remained flat or changed by a relatively small amount since 1990.

Fertilizing crops with the appropriate amount of nitrogen required for optimal crop production, since over-application of nitrogen can lead to higher N2O emissions without enhancing crop production.

Draining water from wetland rice soils during the growing season to reduce CH4 emissions.

Livestock Management

Adjusting feeding practices and other management methods to reduce the amount of CH4 resulting from enteric fermentation.

Improving pasture quality to increase animal productivity, which can reduce the amount of CH4 emitted per unit of animal product. Also, increased productivity in livestock can be introduced through improved breeding practices.

Manure Management

Controlling the way in which manure decomposes to reduce N2O and CH4 emissions.

Capturing CH4 from manure decomposition to produce renewable energy.

Handling manure as a solid or depositing it on pasture rather than storing it in a liquid-based system such as a lagoon. This would likely reduce CH4 emissions but may increase N2O emissions.

Storing manure in anaerobic containment areas to maximize CH4 production and then capturing the CH4 to use as an energy substitute for fossil fuels.

For more information, see EPA's AgSTAR Program, a voluntary outreach and education program that promotes recovery and use of methane from animal manure.

Land Use, Land-Use Change, and Forestry Sector Emissions and Sequestration

Plants absorb carbon dioxide (CO2) from the atmosphere as they grow, and they store some of this carbon throughout their lifetime. Soils can also store some of the carbon from these plants depending on how the soil is managed and other environmental conditions (e.g., climate). This storage of carbon in plants and soils is called biological carbon sequestration. Because biological sequestration takes CO2 out of the atmosphere, it is also called a carbon "sink."

Emissions or sequestration of CO2, CH4 and N2O can occur from management of lands in their current use or as lands are converted to other uses. Carbon dioxide is exchanged between the atmosphere and the plants and soils on land, for example, as cropland is converted into grassland, as lands are cultivated for crops, or as forests grow. In addition, using biological feedstocks (such as energy crops or wood) for purposes such as electricity generation, as inputs to processes that create liquid fuels, or as building materials can lead to emissions or sequestration.*

In the United States overall, since 1990, Land Use, Land-Use Change, and Forestry (LULUCF) activities have resulted in more removal of CO2 from the atmosphere than emissions. Because of this, the LULUCF sector in the United States is considered a net sink, rather than a source, of CO2 over this time-period. In many areas of the world, the opposite is true, particularly in countries where large areas of forest land are cleared, often for conversion to agricultural purposes or for settlements. In these situations, the LULUCF sector can be a net source of greenhouse gas emissions.

Emissions and Trends

In 2016, the net CO2 removed from the atmosphere from the LULUCF sector offset about 11 percent of total U.S. greenhouse gas emissions. Between 1990 and 2016, total carbon sequestration in the LULUCF sector decreased by approximately 9 percent, primarily due to a decrease in the rate of net carbon accumulation in forests and cropland, as well as an increase in CO2 emissions from urbanization.

*Note: The LULUCF sector is a net "sink" of emissions in the United States (e.g., more greenhouse gas emissions are sequestered than emitted from land use activities), so net greenhouse gas emissions from LULUCF are negative.

6,587 million metric tons of CO2 equivalent – what does that mean?

An Explanation of Units

A million metric tons is equal to about 2.2 billion pounds, or 1 trillion grams. For comparison, a small car is likely to weigh a little more than 1 metric ton. Thus, a million metric tons is roughly the same mass as 1 million small cars!

The U.S. Inventory uses metric units for consistency and comparability with other countries. For reference, a metric ton is a little bit larger (about 10 percent) than a U.S. "short" ton.

Greenhouse gas emissions are often measured in carbon dioxide (CO2) equivalent. To convert emissions of a gas into CO2 equivalent, its emissions are multiplied by the gas's Global Warming Potential (GWP). The GWP takes into account the fact that many gases are more effective at warming Earth than CO2, per unit mass.

The GWP values appearing in the Emissions Web pages reflect the values used in the U.S. Inventory, which are drawn from the IPCC's Second Assessment Report (SAR). For further discussion of GWPs and an estimate of greenhouse gas emissions using updated GWPs, see Annex 6 of the U.S. Inventory and the IPCC's discussion on GWPs. Exit